1. Field of the Invention
The present invention relates to a two-stage switching valve in which a large flow rate and a small flow rate can be obtained using a same passageway, and a multistage switching valve in which more than two different flow rates can be switched.
2. Description of the Related Art
In general, in a conventional fluid system in which a small flow rate (e.g., a few cc/min) and a large flow rate (e.g., a few L/min) is switched, a small flow rate valve and a large flow rate valve are provided in parallel, so that the two valves are selectively opened or closed. However, in the conventional arrangement, since the two valves, i.e., the large flow rate valve and the small flow rate valve, the parallel fluid passageways, and a branch connector (tee) provided at a connection portion to connect the parallel passageways are indispensable, the manufacturing cost of the parts is increased and the pipe laying requires a large space and increases the manufacturing cost. In theory, it is possible to switch the large flow rate and the small flow rate by varying the opening angle of a single valve, but it is next to impossible to precisely and instantaneously switch the flow rate, for example, between a few cc/min and a few L/min.